Lower the required Jenkins version

[liejuntao001]

Make it usable for older Jenkins versions

I'd like to use this plugin but the required Jenkins version is too high for me.
I lowered the required version and tested this is working OK.

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your master branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[olamy]

sounds good to me. But maybe there was a reason for such high jenkins version requirement. @jglick any reason?

[jglick]

Intentional (#27). Jenkins will automatically offer you a version of the plugin compatible with your core version (down to 2.263.x, which at this point is not even supported anyway).